Control of swaging temperatures



March 23, 1948. J. H. GREEN 2,438,160

CONTROL 0F SWAGING TEMPERATURES Filed Jan. 19, 1944 F/EK Z5 Z6l mais@ IZ INVENTOR BY www ATTORNEY .esii

Patented Mar. 2li, 1948 UNITED STATES PATENT OFFICE CONTROL F SWAGING TEMPERATURES James H. Green, West Orange, N. J., assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application January 19, 1944, Serial N o. 519,240

6 Claims. (Cl. 236-15) This application is a continuation-in-part of my application, Serial No. 195,490, flied March 12, 1938, now abandoned.

This invention relates to the control of swaging temperatures and, more particularly, to the control 0f the temperature at which rods of refractory metal, such as tungsten or molybdenum, are delivered to a s waging machine for reduction in cross section, as in connection with the manufacture of wire.

The principal object of my invention, generally considered, is the control of the swaging temperature `of a rod of refractory metal by means of the radiations from said rod as it emerges from the furnace on its way tothe swaging machine.

Another object of my invention is the control of swaging temperatures by means of the infrared radiations from the rod or wire as it emerges from the heating furnace on its way to the swaging machine.

A further object of my invention is the control of the swaging temperature of refractory metal by means of a photo-electric cell actuated by the radiations from the heated metal, filtered of substantially all but the infra-red portion, thereby using those which are more accurately proportional to the temperature of the metal, and avoiding, to a great extent, loss in transmission due to dust and smoke.

Other objects and advantages of the invention, relating to the particular arrangement and construction of the various parts, will become apparent as the description proceeds.

In the swaging of tungsten and molybdenum rods and wire, as in manufacturing filaments of tungsten and molybdenum, the metal is heated in gas-fired or electrically-powered furnaces before entering the swaging die. Considerable trouble was experienced in the swaging operation. Control of the temperature, as the rod enters .the die, is necessary to insure uniformity of product and reduce shrinkage. The high order of shrinkage was traceable directly to inadequate temperature uniformity.

In order to cope with this situation, various means of measuring temperature were experimented with, among them, radiation pyrometers, optical pyrometers and thermocouples. None of these performed satisfactorily, as tungsten or molybdenum metal when heated to incandescence oxidizes with extreme rapidity, giving oil dense clouds of vapor which wholly or in part obstruct the vision making it virtually impossible to read or measure temperatures accurately. As a re- 2 sult, controls could not be fitted to any of the above measuring means.

This. then, indicated that an entirely new approach must -be developed which leads to the use of the caesium suboxide photocell. This photocell has an extremely high sensitivity response in the infra-red range, which, when coupled with a filter selected for similar characteristics, gave us a device which would be fairly oblivious to any direct or incidental visible light. By this, I mean to point out that the lter having a visible light transmission of approximately 2% and the photocell itself an exceptionally low response to visible light would combine so as to be practically insensitive to visible radiations.

IJ therefore use a combination of a photo-electric cell and a filter which absorbs substantially all out the infra-red portion of the spectrum, which is impeded very little by smoke and vapor, so that the cell operates only on such portion, and a minimum loss, due to absorption by dust, vapors, and smoke, results. Such filters are known in the art, as referred to in the article by R. A.. Powers, appearing on pages l2 to 15, in-

elusive, of the April 1937 number of Electronics and entitled Phototube temperature control. A "Woods filter, that is, one which absorbs undesired radiation, as manufactured by Corning, is suitable for the purpose. The photo-electric cell or tube and filter unit is desirably constructed so that it has great sensitivity in the near infrared, that is between 7000 and 9000 A. U., and so that it passes only about one percent of the visible radiations.

The above then means that the radiations measured by the cell and iilter combination would be that of infra-red only, which is rather dellnitely known to be absorbed to only a small degree by intervening dust, dirt, oxide fumes, or moisture particles.

The next problem then became one of securing a stablel oscillator which would translate the energy from the photocell into usable energy to actuate a device suitably designed to cause off-on control or a proportionating mechanism to hold the furnace temperatures within a predetermined range. This was accomplished by a vacuum tube bridge circuit to incorporate means of compenstion for tube drift or line voltage fluctuations which, are prime necessities in a control function. The addition of a second tube and suitably selected grid resistors combined with an A. C. rectified voltage-regulated power supply corrected all of the above conditions.

I have, therefore, developed a balanced ampliaaaaiso fier circuit, including a pair of standard radio tubes in push-pull arrangement, to prevent zero drift, and built-in power supply to correct drift troubles and deliver power at a controlled voltage, regardless of line iiuctuation. Temperature control, with tolerances of one percent, is desirably effected by means of a thyratron, a relay, and a reactance operating from the plate circuit of the amplifier, in the case of the electric iurnace, In the case of the gas-tired furnace, a proportionating motor-operated valve is used, with the control box directly connected to a similar amplifying circuit.

In the drawings:

Fig. 1 is a diagrammatic plan view of a gasred furnace, swaging machine, and furnace control mechanism embodying my invention,

Fig. 2 is a corresponding view of a modification in which an electric furnace is substituted for a gas-lired furnace.

Fig. 3 is a wiring diagram of the ampliner used in the embodiments of Figs. l and 2.

Fig. 4 is a wiring diagram of the means for obtaining direct current at a controlled voltage.

Fig. 5 is a wiring diagram of a relay which may be used with the embodiment of my invention shown in Fig. 2.

Fig. 6 is a wiring diagram of the thyratron and circuit, 'which may be used in connection therewith, between the amplifier of Fig. 3 and the relay of Fig. 5.

Referring to the drawings in detail. like parts being designated by like reference characters, and rst considering the embodiment of my invention illustrated in Figs. 1, 3, and 4, there is shown a gas-fired furnace lli through which is passing a rod or wire Ii of refractory material, such as tungsten or molybdenum, in order to be heated to a desired swaging temperature of from 1400 to 1450 C. (for W. 8i Mo) prior to being reduced in section by the swaging machine i2, which may be of a type such as disclosed in the Romanelli Patent No. 2,126,923, dated August 16, 1938. The machine l2 includes swaging dies i3 and feed rollers I4, which latter grip the reduced section I5 of the rod or wire il and draw it through the swaging dies I3.

As the refractory rod il emerges from the iurnace i0, it becomes oxidized by the atmosphere and gives off clouds of vapor, indicated at it. This vapor or smoke absorbs a considerable amount of the visible light emitted from the hot rod, but is not so absorbent to the heat or infra-red rays which are emitted therefrom. Taking advantage of this characteristic, I employ sensitive detecting means, such as a caesium suboxide photoelectric cell ll responding to the range of radiations passed by the Woods filter, which may be one of the type designated "WL-734 and manufactured by the Westinghouse Electric & Manufacturing Company. This is so constructed that it is sensitive to the near infra-red rays. A lter i8 is employed to screen out practically all radiations except those in the infra-red. For this purpose, one such as manufactured by Corning and designated as Heat Transmitting, Old Glass .Y

Code No. 254, New Glass Code No. 2540, may be employed. The cell il and associated filter arrangement are sighted on the rod or wire li, a

ignated as 56, that is a Super-Triode amplifier detector, 2.5 volts, i ampere. These are arranged as illustrated so that tube 20 provides a generally fixed circuit balanced against that provided by tube !9 when the photoelectric cell Il is dark. For .this purpose, the grid circuit of both tubes is energized by the same source of direct current, such as a battery 2l, providing a potential of from 3 to '7 volts and acting through duplicate resistances 22 and 23. Control is obtained by measuring the degree of unbalance as the heated rod passes cell and lilter assembly Il and i8, allowing current to oppose the drop through resistance 22.

The plate circuits of both tubes i9 and 20 are energized by a source of potential applied to the points designated as l and 2 in Fig. 3. In order to secure close regulation of said potential, as is desired, a circuit such as shown in Fig. 4 may be employed. The primary Winding of a, transformer for energizing said circuit is indicated at 2d, said transformer having a secondary winding 25, the ends of which are connected to the anodes 2t and 2l of a full-wave rectifier 28. A rectifier which may be employed is one of those designated as 80, that is a full-wave rectifier, 5 volts, 2 amperes. The mid-point of vthe secondary winding 25 is connected to one side of the secondary circuit as indicated at 29, the other side of said circuit being connected to a secondary Winding 30 which serves to energize the rectier cathodes 3| and 32 in series.

In order to stabilize the output of the arrangement, condensers 33 and @Il are connected across the line and between them is inserted an iron core choke 35, as illustrated. The final control of the potential is by a voltage regulating diode '36 connected through a resistance 3l to an adjustable or bleeder resistance 38 across the output line. In this Way it is possible with an input potential of, say, 110 volts alternating current to deliver a substantially constant potential of, say. volts direct current to the plate circuits for the tubes i@ and 26.

The plates of both tubes i9 and 20 are connected through iixed resistances 39 and il@ and variable resistance di, the positive side of the potential supplied at l and 2 being connected to an intermediate point on the variable resistance 4i as indicated at d2, the arrow representing a slider movable along the resistance element QI to vary the proportion at opposite sides. The negative side of the potential l and 2 is connected to the mid-point between the indirectly heated cathodes 43 and dit of the tubes i9 and 20, said point of connection being desirably grounded as indicated at d5. The heater laments d6 and di of the tubes i9 and 2li are desirably energized .by a supplemental secondary winding d8 of the same transformer. of which coil 2t is the primary, by connection to points 3 and d as shown in Fig. 3.

The output from the circuit illustrated in Fig, 3 is desirably delivered to a recording null potentiometer system of the Leeds & Northrup type, designated as 6l in Fig. 1, which is in turn electricahy connected to the controller i9 of a Minneapolis-Honeywell proportionating system as indicated; that is, through fixed resistance 50, variable resistance 5i, and connecting leads 52 and 53 from the plates of tubes i9 and 20. The variable resistance 5I provides for adjustment so that the controller i9 acts to the desired extent on the proportionating motor through the wires 55, 5d, and 5i to cause said motor to run one Way or the other, in accordance with the condition of the amplifier circuits, as determined by the energization of the photoelectric cell Il, so that if the energization of said cell decreases, on account of the temperature of the rod Il decreasing and the radiation therefrom correspondingly decreasing, the balance of the controller is upset and the proportionating motor operated in one direction, until the increased fuel supply provided through the proportionating valve 58, mixer 59 and manifold 60 increases the temperature of the rod to such an extent that the controller again becomes balanced and the operation of the motor is arrested.

If, on the other hand, the rod II becomes too hot, the grid circuit of the tube I9 overbalances that of the tube 20, resulting in an operation of' the controller in the opposite manner, causing the proportionating motor to operate in the opposite direction and reduce the fuel supply through the proportionating valve 58, thereby correspondingly reducing the temperature of the furnace and the rod heated thereby.

Referring now to the embodiment of my invention illustrated in Figs. 2 to 5, inclusive, there is shown an electrically heated furnace Illa through which is passing a rod or wire Ila of refractory material, such as tungsten or molybdenum, for the purpose of heating the same to a desired temperature, prior to its being reduced in section by a swaging machine I2, which may correspond with the machine I2 of the preceding embodiment.

A photo-electric cell Iln is employed with a filter I8, both of which may correspond with the elements designated as I1 and I8 of the preceding embodiment, said cell being sighted on the rod IIil as it emerges from the furnace Illa in order that it will receive infra-red rays, which are generated by the hot rod or Wire II.

As in the first embodiment, I prefer to use an amplifier 9s having a circuit which may correspond with the amplifier 9 of the rst embodiment as shown in Fig. 3. In the present instance, however, the output from the amplifier circuit is connected to a potentiometer or other direct reading contact device BI, which not only shows the temperature of the rod or wire II, but makes a contact to actuate a relay 62, the circuit in which is shown in Fig. 5. When the control circuit becomes unbalanced, as by a reduction in the desired temperature in the rod or wire II, the solenoid or magnet 63 is energized by closing of the contact in 6 I, drawing the armature 64 thereto and closing a circuit through the auto-transformer 65, thereby effectively decreasing the impedance 66 in the power line 61 to the resistance winding 68 in the electric furnace Ill, and increasing the temperature of said winding. with a corresponding increase in the temperature of the rod or wire I I* heated thereby.

When the control circuit again becomes balanced, thcrelay magnet 63 releases, throwing the impedance 66 again into the circuit and allowing the temperature to correspondingly drop. It will be understood that the arrangement is desirably such that the furnace is a little too hot when the impedance 66 is out of the circuit and a little too cool when it is in the circuit, so that throwing it in and out by the relay magnet 63, actuated by the circuit in the amplifier 9", and the secondary winding 69 of transformer 10, as required, will keep the temperature to which the rod or wire Il* is heated substantially constant.

Referring now to the embodiment of my invention illustrated in Figs. 2 to 6, inclusive, there is shown an arrangement exactly like that of Figs. 2 to 5, inclusive, except that the thvratron 12 and circuit of Fig. 6, replaces the potentiometer and contact device 6I, in the connection between the amplifier circuit of Fig. 3 and the relay 62.

In other Words, the relay leads 52 and 53 connect with the correspondingly numbered leads shown in Fig. 6, which in turn connect respectively to the grid 'II of a thyratron 12, which may be of the type designated as KU-636, as manufactured by the Westinghouse Electric 8: Manufacturing Company. or similar grid-controlled, half-wave rectifier of the gaseous type. The lead 53 is connected through a resistance 73 to this grid 1I, and to the control pointer 'I4 ofl a rheostat '15. The rheostat 'I5 is connected across the terminals of the secondary winding I6 of a transformer 1l, the primary winding of which is designated as 16 and is connected across the line. The cathode 'I9 of the thyratron 'I2 is energized by suitable secondary winding 8O of the transformer 11, the mid-point of which is connected to the adjacent end of the rheostat 15 and one side of the line which energizes the primary windingja by conductor 8I. The other side of the line `is connected by conductor82 to terminal Bof the relay 62, terminal 5 being connected tothe plate 83 as by means of conductor 84. With this arrangement, the thyratron I2 merely replaces the contact device BIa in actuating the relay 62, so that the action of this embodiment is similar yto that of the embodiment of Figs. 2 to 5, inclusive.

From the foregoing, it will be seen that I have devised a method and apparatus for controlling the temperature at which rods or wires of refractory metal, such as tungsten or molybdenum, are heated prior to swaging, whereby a greater uniformity of the product is obtainable and shrinkage reduced.

Any one of three systems may be used, as policy demands. The first system shown in Figs. l, 3 and i, desirably involves the employment of a recording null potentiometer system, which may be of the Leeds and Northrup type, in conjunction with a Minneapolis-Honeywell or other type ci proportionating system which controls or proportions the fuel supply, as by throttiing, in accordance with the demand or load. Such a system is disclosed for a glass furnace in the Richardson et al. Patent No. 2,116,450, of May 3, 1938. The second involves the employment of a contact which measures the drop across an ampliiier circuit, as indication of the temperature, and has a contact arrangement which may be inserted between the pointer and the zero portion thereof and adjusted over the entire range of the instrument for fixing the point at which a relay operates to regulate the heating of an electric furnace. Ihe third involves the replacement of the contact galvanometer by a. thyratron, which when it acts, serves to energize the same relay.

Although preferred embodiments of my invention have been disclosed, it will be understood that modifications may be made within the spirit and scope ofthe appended claims.

I claim: y 1. In combination, a furnace for heating metal, means for supplying heat to said furnace, controlling means for said heat supplying means, a photoelectric cell receiving radiations from said metal as it issues from said furnace. means filtering the visible portion of said radiations so arcaico that substantially nothing but the infra-red portion reaches the photoelectric cell, means connecting said cell to said controlling means through an amplifying circuit for maintaining constant the .temperature of said furnace and issuing metal, a pair of tubes in said circuit, each tube containing a thermionic cathode, a grid, and a plate, means electrically connecting said tubes in balanced relation, including a direct connection between the cathodes and a connection between the grids through a resistance, a source of biasing potential impressed between the midpoint of said resistance and said cathode connection, means connecting said plates to said controlling means and also through a variable resistance, said photoelectric cell being connected to the grid of one tube and to an intermediate point on the variable plate resistance, and a voltage-regulating diode with bleeder and series resistances forming a closely-regulated source of potential impressed between said direct cathode connection and the connection from the cell to said intermediate plate-resistance point.

2. In combination, a furnace for heating elongated pieces of metal, means foi` firing said furnace comprising a mixer for fuel and air, a proportionating valve controlling said mixer, a proportionating motor adapted tra,V run one way or the other, a controller for said motor, a photoelectric cell placed to receive temperature-induced radiations from said metal as it issues from said furnace, .a lter disposed between said cell and metal for absorbing practically all but the infrared radiations from said metal, and amplifying apparatus between said cell and controller for operating the latter to cause the proportionating motor to move the valve toward open position and increase the heat of the furnace if the infra-red radiations reaching the photoelectric cell decrease below a predetermined intensity, and move the valve toward closed position and decrease the heat of the furnace if they increase beyond a predetermined intensity, for maintaining practically constant the temperature of the furnace and issuing metal, 'said apparatus including a pair of radio tubes, each tube containing `a thermionic cathode, a grid and a plate, conductors making a direct connection between the cathodes and a connection between the grids through aresistance, a biasing source of direct current connected between the midpoint of said resistance and the connection between the cathodes, a plate resistance, leads connecting said plates to said controller 'in parallel with said resistance, leads connecting the cathode of the photoelectric cell to the grid of one tube and the anode to an intermediate point on said plate resistance to allow for variation of the latter on opposite sides of said connection, and a voltage-regulating diode with bleeder and series resistances forming alclosely-regulated source of potential connected between said direct cathode connection and the lead from the cell to said intermediate plate resistance point.

3. In combination, an electric furnace for heating elongated pieces of metal, a power circuit toV said furnace, a transformer with a winding in said circuit, a relay armature and contact in circuit with said transformer, a solenoid for operating said armature, a switch for said solenoid, y

amplifying apparatus between said cell and switch for causing the relay armature to engage its Contact, decrease the impedance in the power circuit, and increase the heat of the furnace if the infra-red radiations reaching the photoelectric cell decrease below a predetermined intensity, and disengage its contact, increase the impedance in the power circuit, and decrease the heat of the furnace, if they increase beyond a predetermined intensity, for maintaining constant the temperature of the furnace and issuing metal, said apparatus including a pair of radio tubes, each tube containing a thermionic cathode, a grid and a plate, conductors connecting said tubes in balanced relation including a direct connection between the cathodes and a connection between the grids through a resistance, a biasing source of direct current connected between the midpoint of said resistance and the connection between the cathodes, a plate resistance, leads connecting said plates to said contact device in parallel with said resistance, leads connecting the cathode of the photoelectric cell to the grid of one tube and the anode to an intermediate point on said plate resistance to allow for variation of the latter on opposite sides of said connection, and a voltageregulating diode with bleeder and series resistances forming a closely-regulated source of potential connected between said direct cathode connection and the lead from the cell to said intermediate plate resistance point.

4. In combination, a furnace for heating rods of refractory metals, such as tungsten and molybdenum, to swaging temperatures of from 1400D to l450 C., in which heating operation clouds of oxide are evolved making control by visible radiations inaccurate, means for supplying heat to said furnace, controlling means for said heatsupplying means, a caesium suboxide photoelectric cell placed to receive radiations from said rods as they issue from said furnace, a lter of suchy a character and disposed between the issuing rods and said cell so that substantially nothing but infra-red radiations reach the latter, making the arrangement substantially insensitive to visible light, an amplifying system disposed between and connecting said cell to said controlling means, said system including a pair of tubes each containing a tliermionic cathode, a grid, and a plate, means electrically connecting said tubes in balanced relation, including a direct connection between the cathodes and a connection between the grids through a resistance, a source of biasing potential impressed between the midpoint of said resistance and said cathode connection, means connecting said plates through a variable resistance and also to said controlling means, said photoelectric cell being connected to the grid of one tube and to an intermediate point on the variable plate resistance, and a voltageregulating diode with bleeder and series resistances forming a closely-regulated source 0f potential impressed between said direct cathode connection and the connection from the cell to said intermediate plate-resistance pointfwhereby the rods issue at a substantially constant temperature.

5. In combination, a furnace for heating rods of refractory metals, such as tungsten and molybdenum, to swaging temperatures of from i400 to 1450" C., in which heating operation c1ouds of oxide are evolved making control by visible radiations inaccurate, means for firing said furnace comprising a mixer for fuel and air, a propor-A tionating valve controlling said mixer, a proportionating motor adapted to run one way or the other, a controller for said motor, a caesium suboxide photoelectric cell placed to receive temperature-induced radiations from said rods as they issue from said furnace, a filter of such a character and disposed between the issuing rods and said cell so that substantially nothing but infra-red radiations reach the latter, making the 4 a plate, conductors making a direct connection between the cathodes and a connection between the grids through a pair of fixed equal resistors directly connected, a biasing source of direct current connected directly between said direct connection and the connection between the cathodes, a plate resistance, leads connecting said plates to said controller in parallel with said resistance, leads connecting the cathode of the photoelectric cell to the grid of one tube and the anode to an intermediate point on said plate resistance to allow for variation of the latter on opposite sidesV of said connection, and means providing a closelyl regulated source of potential connected'between the direct cathode connection and the lead from.

the cell to an intermediate plate resistance point, whereby the rods issue at a substantially constant temperature.

6. In combination, an electric furnace for heating rods of refractory metals, such as tungsten and molybdenum, to swaging temperatures of from 1400 to 1450 C., in which heatin'g operation clouds of oxide are evolved making control by visible radiations inaccurate, a power circuit for supplying heat to said furnace, a

transformer with a winding in said circuit, a relay armature and contact in circuit with said transformer, alsolenoid for operating said armature, a switch for said solenoid, a caesium suboxide photoelectric cell placed to receive temperature-induced radiations from said rods as they issue from said furnace, a filter of such a lcharacter and disposed between the issuing rods and said cell -so that substantially nothing but infra-red radiations reach the latter, making the arrangement substantially insensitive to visible light, and amplifying apparatus between said cell and switch for causing the relay armature to engage its contact, decrease the impedance in the power circuit, and increase the heating of the lfurnace if the infra-red radiations reaching the photoelectric cell decrease below a predetermined intensity, and disengage its contact, increase the impedance in the power circuit, and decrease the heat of the furnace if they increase l :beyond a predetermined intensity, said apparatus including a pair of radio tubes, each containing a thermionic cathode, a grid and a plate, conductors connecting said tubes in balanced relation including a direct connection between the cathodes and a connection between the grids through a resistance, a biasing source of direct current connected between the midpoint of said resistance and the connection Ibetween the cathodes, a plate resistance, leads connecting said plates to said contact device in parallel with said resistance, leads connecting the cathode of the photoelectric cell to the grid of one tube and the anode to an intermediate point on said plate resistance to\ all ow for variation of the latter on opposite sides of said connection, and means providing a closely-regulated source of potential connected between said direct cathode connection and the lead from the cell to said intermediate plate resistance point, whereby the rods issue at a substantially constant temperature.

JAMES H. GREEN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,165,037 Tarbox Dec. 21, 1915 1,578,280 Gibson Mar. 30, 1926 1,834,905 Sheldon Dec. 1,'1931 1,937,420 Wood Nov. 28, 1933 1,964,365 Razek June 26, 1934 2,013,594 Zworykin v Sept. 3, 1935 2,041,029 Stargardter May 19, 1936 2,068,574 Smith Jan. 19, 1937 2,089,015 Bucknam et al. Aug. 3, 1937 2,097,502 Southgate Nov. 2, 1937 2,116,450 Richardson et al. May 3, 1938 2,122,941 Hufier July 5, 1938 2,143,672 Archibald Jan. 10, 1939 2,150,017 Barnard Mar. 7, 1939 2,166,824 Runaldue July 18, 1939 2,187,613 Nichols Jan. 16, 1940 2,201,417 Webster May 21, 1940 2,205,182 -Whitten June 18, 1940 OTHER REFERENCES Ballard, Infrared sensitivity of cesium oxide photoelectric cells, Journal of the Optical Society of America, vol. 20, Nov. 1930, pages 618- 623 inc,

Powers: Phototube temperature control, Electronics, Apri1 1937, pages 12-15 inc. 

